Marine vessels frequently employ electronically controlled engines in which throttle and shift are controlled, at least in part, electronically. In such engines, throttle is typically controlled by controlling the output of a potentiometer. Specifically, operation of a throttle control lever, typically located at the bridge, causes rotation of a shaft coupled to a potentiometer so that rotation of the shaft varies the output of the potentiometer. The output of the potentiometer is transmitted to a controller that causes the throttle to vary (i.e., increase or decrease) according to the potentiometer output. Similarly, operation of a shift control lever, which is also typically located at the bridge, causes rotation of a shaft coupled to a potentiometer, the output of which is transmitted to a controller that causes the shift position to vary according to the potentiometer output.
It is well known that operators of such marine vessels like the feel of hydraulic controls. Consequently, marine vessels are frequently equipped with hydraulic controls. The use of hydraulics to control electronically controlled engines via mechanical linkages is well-known and common among large marine vessels. In such systems, operation of a control lever at the bridge sends an hydraulic signal to an hydraulic slave cylinder in the engine compartment. Levers and linkages then convert the motion of the hydraulic slave cylinder's piston into rotation of the potentiometer shaft. Although this approach is workable, it frequently results in lost motion and, therefore, inaccuracies in the throttle control function. Hence, there is a need in the art for improved hydraulic-electronic control systems that convert hydraulic motion into rotational motion for electronic control of shift position and throttle without the need for such levers and linkages.